After a weekend of intense investigation , authorities are piecing together more details about Friday 's fatal shooting at Los Angeles International Airport , including the suspect 's behavior earlier in the week and a warning from his family that may have come minutes too late .

Officers sent to check on Paul Ciancia 's welfare arrived at his apartment less than an hour after the shooting started , police said Monday .

Here is a rundown to get you up to speed :

The suspect

Ciancia , 23 , of Los Angeles , is charged with murder of a federal officer and commission of violence in an international airport .

He was shot by officers Friday and was in critical condition at Ronald Reagan UCLA Medical Center on Sunday .

A source said Ciancia was unable to speak to investigators .

Clues about a motive

Attorney General Eric Holder said Monday that more investigation is necessary to uncover a motive for the attack .

But a note found on Ciancia indicated that he wanted to kill Transportation Security Administration employees to `` instill fear '' in what the suspect called the agents ' `` traitorous minds , '' FBI Special Agent in Charge David Bowdich said .

According to someone who knew Ciancia and his three roommates well , Ciancia began asking for a ride to the airport days before the shooting . He claimed he needed to fly to New Jersey to help his sick father , but he never said what day he needed to leave , the source said .

On Friday , Ciancia burst into a roommate 's room and demanded a ride to the airport immediately , said the source , who spoke to CNN on the condition of anonymity .

The roommate obliged . Investigators do n't think the roommate had any idea of Ciancia 's plans .

The near-save

Around the same time , Ciancia was sending text messages to family members in Pennsville , New Jersey .

One suggested that something bad would happen .

Although Ciancia has no known history of mental illness , he said in the texts that he was unhappy , and the messages were alarming enough that Ciancia 's father decided to call police .

`` I felt that it was pretty serious . It sounded as if Paul Ciancia in California was thinking about harming himself , so obviously I knew I needed to make a phone call to the LAPD , '' Pennsville Police Chief Allen Cummings told CNN 's Jake Tapper on Monday .

Cummings spoke with a lieutenant there , who told him the department was in the middle of responding to a shooting at LAX .

`` At this point , we were n't connecting the dots , '' he said . They did later when a reporter called the police chief , asking him to comment on the shooting .

Los Angeles Police Department Cmdr. Andy Smith says police were first called to check on Ciancia at 10:06 a.m. Officers arrived at his apartment six minutes later , according to Smith .

Ciancia was already gone .

The timeline provided Monday by police differed from that offered earlier by Rep. Michael McCaul , R-Texas , chairman of the House Homeland Security Committee . He said police had arrived at Ciancia 's apartment about 45 minutes after the suspect had left for the airport .

According to the LAPD account , they arrived 52 minutes after the shooting , which began about 9:20 a.m. , according to police . It was not immediately clear when Ciancia left for the airport .

The attack

About 9:20 a.m. Friday , Ciancia walked up to a Transportation Security Administration checkpoint in Terminal 3 . He pulled a .223 - caliber assault rifle from a bag and shot TSA officer Gerardo Hernandez `` at point-blank range , '' according to a court document filed by an FBI agent .

Ciancia then went up an escalator but returned to shoot Hernandez again , apparently after seeing him move .

He continued walking and shooting . Witnesses said he went from person to person , asking , `` Are you TSA ? ''

`` I just shook my head , '' traveler Leon Saryan told CNN 's Anderson Cooper . `` And he kept going . ''

Chaos and terror inside LAX Terminal 3

The victims

Hernandez , 39 , was the first TSA officer to die in the line of duty since the agency was created in 2001 .

`` He took pride in his duty for the American public and for the TSA mission , '' said his wife , Ana Hernandez .

The couple , who married in 1998 , have two children .

Two other TSA officers -- James Speer , 54 , and Tony Grigsby , 36 -- were wounded but were released from the hospital .

Grigsby , who was shot in the foot , told reporters Monday he was injured while helping an elderly man move to a safe area .

`` I turned around and there was a gunman , '' he said . `` Shot me twice . ''

A traveler who was shot in the leg , 29-year-old Brian Ludmer of Lake Forest , Illinois , was in fair condition Sunday .

The police response

TSA officers are unarmed . So it was airport police officers who eventually shot Ciancia multiple times in the chest , also striking him in the face and neck .

Airport Police Chief Patrick Gannon said the FBI told him that his officers were 60 seconds behind Ciancia . He praised their response , even though he acknowledged that he had moved his officers away from positions inside the checkpoints during the past year .

`` The threat ... at the airport does not exist behind security at that podium ; the threat exists from the curbline on , '' Gannon said . `` So ... we have our people stationed throughout the airport . ''

Holder said Monday that the investigation will include a review of security measures at LAX and other airports .

`` The responsibility for protecting airport security is not a TSA function but something that I think we need to certainly examine , given what happened in Los Angeles , '' he said .

Travel delays

The incident forced authorities to shut down parts of the airport , evacuate travelers and put a temporary hold on some departures and landings .

More than 167,050 airline passengers were affected by the incident Friday as a result of cancellations , delays or diversions to other airports , according to LAX . One airline , JetBlue , temporarily moved its operations to Long Beach Airport .

On Saturday , an additional 40 flights were affected , including 30 that were canceled , involving about 4,000 passengers , according to Los Angeles International Airport .

According to FlightAware , a flight tracking website , airlines canceled 236 flights into or out of LAX after the incident Friday morning and 27 more Saturday .

An additional 919 flights were delayed over the two days , FlightAware said .

Some of those cancellations and delays may have been caused by problems other than the shooting , however .

The airport was operating normally Monday morning .

Suspect 's family responds

Ciancia 's family , in a statement read Monday afternoon by attorney John Jordan in New Jersey , said they were `` shocked and numbed by the tragic events of last Friday . ''

`` It is most important for us as a family to express our deep and sincere sympathy to the Hernandez family , '' the Ciancia family said . '' -LRB- By -RRB- all accounts , Officer Hernandez was an exemplary member of the law enforcement community and a good family man . Our hearts go out to his family and many others who grieve his passing .

`` We wish to convey , too , our hopes that those who were wounded during this incident will experience quick and full recoveries . We also regret the inconvenience experienced by thousands of travelers as well as the administration and the employees of the Los Angeles airport . ''

The Ciancia family said they would `` continue to love and care for '' Paul .

`` We will support him during the difficult times ahead . While we do not mean to minimize the grief and distress experienced by many other families , we hope that the public will understand that this is a very difficult time for our family , too , '' the family said .

What 's next ?

If convicted , Ciancia could face the death penalty or life in prison without parole . The U.S. attorney general would decide whether to pursue a death sentence .

TSA Administrator John Pistole said the shooting has prompted a review of security protocol with partner agencies .

McCaul said better coordination with local law enforcement could improve security at checkpoints .

But the congressman acknowledged that `` it 's very difficult to stop these types of attacks . ''

`` It 's almost like an open shopping mall , '' he said .

Opinion : Do n't arm the TSA

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An injured officer says he was shot while trying to help an elderly man move to safety

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LAPD provides timeline for welfare check at suspect 's home

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Suspect Paul Ciancia , 23 , is in critical condition and could face the death penalty

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Police responded to family concern , arrived at Ciancia 's apartment shortly after he left